Review SL: CIS Second Semester Chemistry Exam 2016
Terms in this set (43)
Elements tend to lose, gain, or share electrons to acquire a noble gas core e- configuration.
The energy required to completely separate a mole of a solid ionic compound into its gaseous ions.
Increases with the charge on the ions and also increases with decreasing size of ions.
The strength of a bond measured by determining how much energy is required to break the bond.
- Average bond enthalpies are positive, because bond breaking is an endothermic process.
Polar Covalent Bonds
Although atoms often form compounds by sharing electrons, the electrons are not always shared equally.
The ability of atoms in a molecule to attract electrons to itself.
increases as you go...
➢ ...from left to right across a row.
➢ ...from the bottom to the top of a column.
The greater the difference in electronegativity, the more polar is the bond.
Exceptions to the Octet Rule
1. Ions or molecules with an odd number of electrons.
2. Ions or molecules with less than an octet.
3. Ions or molecules with more than eight valence electrons (an expanded octet)
Bigger than other pairs, therefore, their repulsions are greater; this tends to decrease bond angles in a molecule.
The two things the state a substance depends on.
1. Kinetic Energy
2. Strength of attraction between particles
Between atoms or molecules (weaker than intramolecular which is between compounds)
van de Waals forces
Intermolecular forces as a group (most to least):
1. Hydrogen Bonding
2. Dipole-Dipole interactions
3. London Disepersion forces
Molecules that have permanent dipoles are attracted to each other.
The positive end of one is attracted to the negative end of the other and vice- versa.
These forces are only important when the molecules are close to each other.
The more polar the molecule, the higher is its boiling point.
London Dispersion Forces
Attractions between an instantaneous dipole and an induced dipole.
These forces are present in all molecules, whether they are polar or nonpolar.
- Long Skinny molecules tend to have stronger dispersion Forces due to increased surface area
- Strength increases with increased molecular weight
- Larger atoms have larger electron clouds that are easier to polarize
Dispersion vs Dipole forces
Only when one molecule is larger than another will dispersion forces be likely stronger than dipole
Dipole-Dipole interactions between H and N, O, or F
Viscosity and intermolecular forces
Viscosity increases with stronger intermolecular forces and decreases with higher temperature.
Allotropes of Carbon
➢ Graphene ➢ C60 fullerene
Sea of Electrons: Electrons are delocalized throughout the solid.
The change in the concentration of a reactant or a product with time (M/s).
A -> B
Rate = - ∆[A] / ∆t ( [A]decreases with time, thus it's negative)
Rate = ∆[B] / ∆t
t = time |A and B = concentration
Factors that affect reaction rates
- Presence of catalyst
- Concentration of reactants (likelihood of collision increases with concentration)
- State of Reactants (particles size and homogenous mixtures react faster)
Reaction Rate and Stoichiometry
2A -> B
Rate = - (1 / 2) ∆[A] / ∆t
Rate = ∆[B] / ∆t
General Idea of Rate Reaction
aA -> bB
Rate = - (1/a) ∆[A] / ∆t = (1/b) ∆[B] / ∆t
A substance that increases the rate of reaction without being consumed
-Decreases activation energy
The measure of temperature is the average kinetic energy of the molecules in the same, as there is a wide distribution of kinetic energies between molecules
As temperature increases the curve flattens and a larger portion of molecules have high energy
Reaction Rate increases with higher temperature (More molecules can pass the energy barrier needed to achieve the reaction)
k = rate / [A]
k = slope of the reaction
Occurs when a reaction and its reverse reaction proceed at the same rate.
As a system approaches equilibrium both the forward and reverse reactions are happening
Once equilibrium is reached the amount of product and reactant remains constant
Concentrations of solids and liquids are constant (to be ignored)
For a reaction in reverse, the equilibrium constant is the reciprocal (switch denominator and numerator)
For a reaction multiplied by a number, the equilibrium constant becomes raised to the power of that number
Value of K
K > 1
K < 1
Equilibrium constant calculation
Given two initial concentrations of reactants, and the concentration of a product at equilibrium.
The concentration of the reactant marks the overall change, divide by subscript for 1 stoich unit and subtract two initial concentrations
Using the given equilibrium values, use equilibrium constant
Reaction Quotient (Q)
Similar to Equilibrium constant, but for a system not at equilibrium
Le Chatelier's Principle
If a system at equilibrium is disturbed by a change in temperature, pressure, or the concentration of one of the components, the system will shift its equilibrium position so as to counteract the effect of the disturbance.
Changes in Temperature:
Exothermic - Raising Temperature - Shifts Left
A -> <- B + heat
Endothermic - Raising Temperature - Shifts Right
heat + A -> <- B
Concentration increase on the reactant side shifts equilibrium right, vice versa
Increasing pressure results in equilibrium shift to side with less moles
A -> <- 2B - Shifts Left
Substance that when dissolved in water increases the concentration of hydrogen ions (H+)
Substance that when dissolved in water increases the concentration of hydroxide ions (OH-)
Bronsted Lowry Acid
must have a removable (acidic) proton
Bronsted Lowry Base
must have a pair of nonbonding electrons
Either Bronsted Lowry or Base: Can both donate protons or accept them
Conjugate Acid: The conjugate that gains a proton (H3O+)
Conjugate Base: The conjugate that loses a proton (HSO4-)
(Protons are mostly in form of H+)
Strong Acid Vs Weak Acid
Strong acids dissolve completely in water whilst weak acids only dissolve partially
Weak acids dissolve only partially because unlike strong acids, their conjugate bases are quite strong and do not dissociate in water
Measure of how acidic/basic H3O+ is
pH = -log [H3O+]
(H3O+ concentration needed)
pH < 7
pH > 7
(7 being the pH of pure water)
Other ways to Measure pH?
• "Red" paper turns
blue above ~pH = 8
• "Blue" paper turns
red below ~pH = 5
pH meter: measures voltage in a solution
HCl, HBr, HI, HNO3, H2SO4, HClO3, and HClO4.
Strong bases are the soluble hydroxides, which are the alkali metal and heavier alkaline earth metal hydroxides (Ca2+, Sr2+, and Ba2+)
Boiling Point and Electronegativity
The greater the difference in electronegativity, the higher the boiling point
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